Both plastic and metal closures for various bottles and containers which include a tamper-evident feature have been known for many years. In most cases, this tamper-evident feature comprises a lower shoulder or skirt portion of the closure which is in some way intended to fracture or break upon removal of the closure from the container, so that it then becomes evident that the container has been opened. While a large number of these closures have been known in the past, on a commercial basis, and particularly in connection with soda bottles and other such containers maintained under significant pressures, up until quite recently metal closures have predominated. These include closures such as those shown in U.S. Pat. No. 3,812,991 which issued on May 28, 1974 to the Coca Cola Company, and many others.
The many problems encountered in connection with the use of metal closures however, have been significant. They primarily relate to the fact that in an unacceptably large proportion of cases, removal of the closure does not result in a clean and efficient fracture of the lower skirt portion, therefore making removal of the closure quite difficult and/or eliminating the tamper-evident feature completely. In addition, the cost of metal closures has recently increased dramatically, and the search for efficient plastic closures has therefore intensified.
In connection with plastic closures of this type, again a large number have been known in the past, but no commercial closure has been found which can be applied in a single step to the container or bottle, (i.e., they generally require a two-step application procedure), and can at the time result in efficient breaking or fracturing upon its removal. One recent commercial closure which is now widely utilized is that of U.S. Pat. No. 4,033,472 to Albert Obrist AG, which issued on July 5, 1977. This closure, however, again suffers from both of these infirmities. In the first place it requires a two-step application procedure, i.e., initial application of the closure to the bottle followed by a heating process whereby the lower depending bead 4 is deformed against the surface of the bead or collar on the bottle itself, as shown in FIG. 4 thereof. In addition, it has again been found that these closures, although used commercially, do not fracture properly in an unacceptable proportion of cases. Several other issued patents which include such two-step application procedures include U.S. 3,673,761 assigned to Ciba-Geigy AG, and U.S. Pat. No. 3,788,509 to Keeler, which includes a separate heating step for producing the weakened zones themselves.
Among those patents which do show a one-piece plastic closure, which does not require such a heat sealing step are those to Hamberger, namely U.S. Pat. Nos. 2,162,711 and 2,162,712. These patents, however, are directed to closures which include a weakened portion defined by corresponding grooves on the shoulder portion (see FIG. 1 thereof) of the depending skirt 23. In these closures fracture thus occurs in a vertical direction with respect to the closures and tangentially with respect to the lugs 18 to which the skirt is attached. In addition, the skirt portion in this patent appears to be constructed so as to be thinner than the upper walls thereof. Additional such closures are also known in the Schauer patents, namely U.S. Pat. Nos. 2,162,752 and 2,162,754. Also, U.S. Pat. No. 3,329,295, to Fields, teaches yet another such closure, which is this case includes a cylindrical skirt 17 depending from the free end of side walls 5 by means of circumferentially spaced, fracturable bridges 19. This patent further includes an inwardly directed lip 20 overlapping the annular bead 22 on the container or bottle to which it is to be applied, and requires the maintenance of a gap 26 between shoulder 24 and lip 20. Only a small portion of the cross-sectional thickness of Fields' skirt 17 is located below the outer end of side wall 5 and the wall are therefore not in substantial alignment with each other on either side of the bridges 19 thereof. None of these prior art patents teaches the structure of a truly satisfactory commercially acceptable product.
There are yet another group of patents directed to such closures which rely upon interlocking teeth or serrations in order to effect the fracture of the closure. For example, French Patent No. 1,347,895 includes a ratchet or lug means on the breakaway skirt portion 2 thereof as well as on the bottle bead, and German Pat. No. 2,349,265 also includes lugs 16 which extend inwardly from depending skirt 13 to aid in fracturing at the point of weakness thereon. Reference in this regard is also made to U.S. Pat. Nos. 3,980,195, 3,924,769 and 4,126,240.
Finally, while U.S. Pat. No. 3,784,041 to Birch principally relates to the use of an annular resilient flange 25 extending radially inward from the skirt 13, beginning at column 3, line 60 thereof, and as shown in FIGS. 5-7, a tamper evident closure cap is shown in connection with this sealing arrangement. However, the bridge portions 40 of Birch et al have a radial thickness which varies circumferentially of the closure cap 35, thus increasing in thickness in the direction of arrow 39, in which the closure cap is unscrewed from the neck of the container. Furthermore, the lowermost portion 37 of Birch et al's skirt 36 projects inwardly to a point considerably further than the plane corresponding to the inner surface of the side wall where the bottom of the threads 15 are located. Again, a closure which can truly meet all the commercial requirements for such tamper-evident closures is not shown or suggested therein.